<HTML>
<BODY BGCOLOR="white">
<PRE>
<FONT color="green">001</FONT>    package gates;<a name="line.1"></a>
<FONT color="green">002</FONT>    <a name="line.2"></a>
<FONT color="green">003</FONT>    import register.Register;<a name="line.3"></a>
<FONT color="green">004</FONT>    import gates.FunctionGate;<a name="line.4"></a>
<FONT color="green">005</FONT>    import mathtools.Complex;<a name="line.5"></a>
<FONT color="green">006</FONT>    /**<a name="line.6"></a>
<FONT color="green">007</FONT>     * Functional representation of a iI gate.<a name="line.7"></a>
<FONT color="green">008</FONT>     * This implements Gate interface, so consult this for public methods.<a name="line.8"></a>
<FONT color="green">009</FONT>     * The constructor for this gate is protected, so generating such an object is left<a name="line.9"></a>
<FONT color="green">010</FONT>     * for the factory class &lt;code&gt;Factory&lt;/code&gt;<a name="line.10"></a>
<FONT color="green">011</FONT>     * @author Jan Zaucha<a name="line.11"></a>
<FONT color="green">012</FONT>     */<a name="line.12"></a>
<FONT color="green">013</FONT>    public class ComplexIdentityFunction extends FunctionGate {<a name="line.13"></a>
<FONT color="green">014</FONT>    <a name="line.14"></a>
<FONT color="green">015</FONT>            /** Store the target qubit the gate acts on*/   <a name="line.15"></a>
<FONT color="green">016</FONT>            private int target;<a name="line.16"></a>
<FONT color="green">017</FONT>    <a name="line.17"></a>
<FONT color="green">018</FONT>            /**<a name="line.18"></a>
<FONT color="green">019</FONT>             * Protected constructor for a functional representation of a iI gate<a name="line.19"></a>
<FONT color="green">020</FONT>             * Requires a target bit for the gate to operate on, however if the target bit is<a name="line.20"></a>
<FONT color="green">021</FONT>             * -1 the gate will act on all qubits<a name="line.21"></a>
<FONT color="green">022</FONT>             * @param target the target bit to hadamard transform (counting qubits from 0)<a name="line.22"></a>
<FONT color="green">023</FONT>             */<a name="line.23"></a>
<FONT color="green">024</FONT>            protected ComplexIdentityFunction(int target){<a name="line.24"></a>
<FONT color="green">025</FONT>                    this.target = target; // actually the only special case is when target = -1<a name="line.25"></a>
<FONT color="green">026</FONT>            }<a name="line.26"></a>
<FONT color="green">027</FONT>    <a name="line.27"></a>
<FONT color="green">028</FONT>            /**<a name="line.28"></a>
<FONT color="green">029</FONT>             * Returns the name of the gate regardless of representation.<a name="line.29"></a>
<FONT color="green">030</FONT>             */<a name="line.30"></a>
<FONT color="green">031</FONT>            public String getName() {<a name="line.31"></a>
<FONT color="green">032</FONT>                    return "Complex Identity";<a name="line.32"></a>
<FONT color="green">033</FONT>            }<a name="line.33"></a>
<FONT color="green">034</FONT>    <a name="line.34"></a>
<FONT color="green">035</FONT>            /**<a name="line.35"></a>
<FONT color="green">036</FONT>             * Applies this gate to the given register. See interface &lt;code&gt;Gate&lt;/code&gt; for usage.<a name="line.36"></a>
<FONT color="green">037</FONT>             * @param r the register <a name="line.37"></a>
<FONT color="green">038</FONT>             */<a name="line.38"></a>
<FONT color="green">039</FONT>            public void apply(Register r) {<a name="line.39"></a>
<FONT color="green">040</FONT>                    if (target &gt;= r.getNumQbits() || target &lt; -1){<a name="line.40"></a>
<FONT color="green">041</FONT>                            throw new IllegalArgumentException("Target qubit not in register. Register size (qubits): " + r.getNumQbits() + " Target qubit: " + target);<a name="line.41"></a>
<FONT color="green">042</FONT>                    }<a name="line.42"></a>
<FONT color="green">043</FONT>                    // if target is flagged "-1" we hadamard transform all qubits<a name="line.43"></a>
<FONT color="green">044</FONT>                    if(target==-1){<a name="line.44"></a>
<FONT color="green">045</FONT>                            for(int j=0; j&lt; r.getNumQbits(); j++){<a name="line.45"></a>
<FONT color="green">046</FONT>                                    this.applyToSingleQubit(r);<a name="line.46"></a>
<FONT color="green">047</FONT>                            }<a name="line.47"></a>
<FONT color="green">048</FONT>                    }<a name="line.48"></a>
<FONT color="green">049</FONT>                    // else apply to a given single qubit<a name="line.49"></a>
<FONT color="green">050</FONT>                    else {<a name="line.50"></a>
<FONT color="green">051</FONT>                            this.applyToSingleQubit(r);<a name="line.51"></a>
<FONT color="green">052</FONT>                    }<a name="line.52"></a>
<FONT color="green">053</FONT>            }<a name="line.53"></a>
<FONT color="green">054</FONT>    <a name="line.54"></a>
<FONT color="green">055</FONT>            /**<a name="line.55"></a>
<FONT color="green">056</FONT>             * Private method that applies iI gate to the given register given the target qubit. <a name="line.56"></a>
<FONT color="green">057</FONT>             * @param r the register <a name="line.57"></a>
<FONT color="green">058</FONT>             */<a name="line.58"></a>
<FONT color="green">059</FONT>            private void applyToSingleQubit(Register r){<a name="line.59"></a>
<FONT color="green">060</FONT>                    int numStates = r.getHeight();    // number of states in register<a name="line.60"></a>
<FONT color="green">061</FONT>                    Complex newAmplitude;<a name="line.61"></a>
<FONT color="green">062</FONT>                    for(int j=0; j&lt; numStates; j++){<a name="line.62"></a>
<FONT color="green">063</FONT>                            newAmplitude =  Complex.multiplyComplex(new Complex(0.0, 1.0), r.getElement(0, j));<a name="line.63"></a>
<FONT color="green">064</FONT>                            r.setElement(0, j, newAmplitude);<a name="line.64"></a>
<FONT color="green">065</FONT>                            <a name="line.65"></a>
<FONT color="green">066</FONT>                    }<a name="line.66"></a>
<FONT color="green">067</FONT>                    // normalize register<a name="line.67"></a>
<FONT color="green">068</FONT>                    r.normalise();<a name="line.68"></a>
<FONT color="green">069</FONT>    <a name="line.69"></a>
<FONT color="green">070</FONT>            }<a name="line.70"></a>
<FONT color="green">071</FONT>    <a name="line.71"></a>
<FONT color="green">072</FONT>    }<a name="line.72"></a>




























































</PRE>
</BODY>
</HTML>
